1. Field of the Invention
This invention relates to a rotary member and a fixing device for fixing an unfixed image, particularly to a rotary member having a heat source for heating the rotary member, a rotary member for fixing which fixes an unfixed image onto a recording material by heat and pressure, and a fixing device using it.
2. Related Background Art
In the prior art, for fixing an unfixed image, a rotary member such as belt or roller, etc. has been widely practiced. Particularly, hot roller fixing which fixes an unfixed image by heat and pressure at the nip portion formed between rollers by permitting a carrier having an unfixed image between a pair of fixing rollers as the rotary member for fixing has been the main stream, partially because of simplicity of the device.
Further, for such demands to increase the layer thickness of the unfixed image and the fixing speed during fixing by such fixing rollers, a fixing device provided with elasticity has been proposed.
However, with the fixing rollers of the fixing device as described above, there has been utilized in the prior art silicone rubber, particularly silicone rubber such as TRV, LTV, etc. or those in which an inorganic agent such as red iron oxide is mixed for the purpose of satisfying both elasticity and mold releasability necessary for fixing. However, in the rubber by use of a crosslinking agent such as RTV silicone rubber or LTV silicone rubber, recrosslinking proceeds by heating to make the rubber brittle, or decompose it by thermal oxidation. Also the rubber is swelled with the silicone oil coated as the mold release agent, whereby the outer diameter as the fixing roller partially changes and there is a a problem that deleterious influence is exerted on the fixed image.
In other words, in such fixing roller, as the material satisfying elasticity and mold releasability necessary for fixing and also having sufficient printing resistance, there is no single material, but generally a constitution of plural layers is made by providing a fluorine resin or a silicone resin on a rubber (silicone rubber), thereby endowing the respective layers with functions necessary for fixing.
However, one having as fluorine resin formed as the upper layer suffers from elongation of the fluorine resin by swelling of the roller core metal and the lower layer rubber by heating, and by repetition of this, fine wrinkles will be generated on the roller surface. Also, as disclosed in Japanese Patent Laid-open No. 62-255081 or No. 58-11976, when a silicone resin film is formed by coating a silicone varnish on a rubbery elastomer, the hardness of the film is high, and further the elongation of the varnish is generally low as 50% or lower, whereby marked elongation and shrinkage of the lower layer rubber cannot be followed, with the result that not only cracks are generated but there was also possibility of occurrence of peeling.